Antiviral agent

ABSTRACT

PCT No. PCT/JP86/00383 Sec. 371 Date Mar. 23, 1987 Sec. 102(e) Date Mar. 23, 1987 PCT Filed Jul. 21, 1986 PCT Pub. No. WO87/00435 PCT Pub. Date Jan. 29, 1987.A method of inhibiting viral replication in a cell comprising administering an effective amount of an esterified derivative of 5-halogenated-2&#39;-deoxy-uridine expressed by the following formula (I)   &lt;IMAGE&gt; (I)   wherein X represents any one of F, Cl, and Br; R1 and R2 may be identical or different from each other, each representing an aliphatic acyl group comprising two or more carbon atoms or an aromatic acyl group comprising 7 or more carbon atoms.

TECHNICAL FIELD

This invention relates to an antiviral agent. More particularly thisinvention relates to an antiviral agent which displays a high level ofantiviral effect with small doses and yet its toxicity to normal cellsis low.

BACKGROUND ART

The replication of a viral DNA in a viral infected cell is conductedindependently of the DNA replication cycle of the host cell, and itproceeds at much higher level in both speed and volume as compared withthe replication of DNA which takes place in a normal cell. In view ofthis fact, reports have been made and published on several kinds ofcompounds which inhibit the DNA formation of a virus based on thedifference in the process of DNA replication between a normal cell and avirus infected cell such as (E)-5-(2-bromovinyl)-2'-deoxyuridine[Nucleic Acid Research, 10, 6051 (1982), European Patent Publication No.61283], 2'-nor-2'-deoxyguanosine [Biochemical and Biophysical ResearchCommunications, 116, 360 (1983)], 9-(2-hydroxy-3-nonyl) adenine[Biochemical Pharmacology, 32, 3541 (1983)],9-(2-hydroxyethoxymethyl)guanine [Chemotherapy, 25, 279 (1979), Journalof Biological Chemistry, 253, 8721 (1978)],9-β-D-Arabinofuranosyladenine [British Medical Journal, 2, 531 (1978)],etc.

Besides the aforementioned ones, it is reported that 5-halogenatedpyrimidinenucleoside strongly inhibits the DNA formation in a virusinfected and normal eucaryotic cell [Biochemical and BiophysicalResearch Communications, 86, 112 (1979), Pharmacology Review, 29, 249(1977), Biochemica et Biophysica Acta, 518, 31 (1978), Proceedings ofthe Society for Experimental Biology and Medicine, 154, 439 (1977),Cancer Research, 36, 4480 (1976)]. However, 5-halogenatedpyrimidinenucleoside in its original condition is too strong in itsfunction to inhibit the DNA formation in an animal cell and5-iodo-2'-deoxyuridine has a limited use as an antiviral agent only forherpetic keratitis. Also, 5-fluoro-2'-deoxyuridine is efficacious as anantitumor drug [Cancer Research, 38, 3784 (1978)], and it is alsoreported that its ester derivatives have an antitumor activity [CancerChemotherapy and Pharmacology, 6, 19 (1981), Chemical and PharmaceuticalBulletin, 33, 1652 (1985)]; however, nothing has yet been made knownabout its antiviral activity.

DISCLOSURE OF THE INVENTION

As the result of an intensive research conducted on masked typecompounds obtained by modifying the hydroxyl group of5-halogenated-2'-deoxyuridine with various substituents with the purposeof obtaining a drug of low toxicity for normal animal cell whileinhibiting the proliferation of virus even when taken in small dosage byinducing a compound, which is inhibitive of the DNA formation, intoderivatives, the present inventors have come to find that variouscompounds obtained by esterifying the hydroxyl group of5-halogenated-2'-deoxyuridine with an aliphatic or aromatic acyl groupnot only display the effect of inhibiting the proliferation of virus athigh level when taken in very small dosage but also show a hightherapeutic index while having a low toxicity against normal cells, thuscompleting the present invention.

The present invention relates to an antiviral agent characterized bycontaining as an active ingredient an esterified derivative of5-halogenated-2'-deoxyuridine expressed by the following formula (I)##STR2## wherein X represents any one of F, Cl and Br; R¹ and R² may beidentical or different from each other, each representing an aliphaticacyl group comprising two or more carbon atoms, or an aromatic acylgroup comprising seven or more carbon atoms.

BEST MODE OF CARRYING OUT THE INVENTION

In the formula (I) of this invention, X represents F, Cl or Br, of whichF and Cl are preferable.

R¹ and R² are identical or different from each other, each representinga hydrogen atom, or an aliphatic acyl group comprising two or morecarbon atoms, or an aromatic acyl group comprising six or more carbonatoms.

As the aliphatic acyl group of this type, acetyl, butyryl, hexanoyl,octanoyl, decanoyl, dodecanoyl, tetradecanoyl, and hexadecanoyl, forinstance, may be mentioned, and as the aromatic acyl group, there arebenzoyl, toluoyl, and naphthoyl.

As the concrete examples of this invention, there are, for instance,3',5'-dioctanoyl-5-fluoro-2'-deoxyuridine,3',5'-didodecanoyl-5-bromo-2'-deoxyuridine,3'5'-ditetradecanoyl-5-fluoro-2'-deoxyuridine,3',5'-dihexanoyl-5-fluoro- 2'-deoxyuridine,3',5'-didecanoyl-5-fluoro-2'-deoxyuridine,3',5'-didodecanoyl-5-fluoro-2'-deoxyuridine,3',5'-dihexadecanoyl-5-fluoro-2'-deoxyuridine,5',5'-dibenzoyl-5-fluoro-2'-deoxyuridine, and3',5'-ditoluoyl-5-fluoro-2'-deoxyuridine.

The compounds of this invention can all be synthesized according to anyknown method such as the one shown in the Biochemical Pharmacology, 14,1605 (1965). For example, their synthesis can be achieved according toan ordinary method in which 5-halogenated-2'-deoxyuridine is allowed toreact with a corresponding acid halide or acid anhydride in the presenceof such an organic base as pyridine and trialkylamine.

When the compound expressed by formula (I) according to this inventionhas its antiviral effect examined by observing its activity ofdecreasing the number of plaque forming cells with the use of Vero cells(cell system obtained by inoculating the strain African green monkey'skidney cells with the herpes simplex type I), the result shows that itdisplays a strong inhibitory effect against the proliferation of viruswhen it is taken in a very small dose equivalant to 1/15 to 1/400 of9-(2-hydroxyethoxymethyl) guanine (Acyclovir) and that the minimum toxicdose to cells is as high as 1,500 to 10,000 times the density at whichit displays the inhibitory effect against the proliferation of virus.When compared with 5-fluoro-2'-deoxyuridine, which is an underived formof 5-halogenated-2'-deoxyuridine, the compound of formula (I) has theminimum toxic dose against cells as high as 1,000 times and shows anexcellent therapeutic index while its antiviral effect is at the samelevel.

For instance, 3',5'-dioctanoyl-5-fluoro-2'-deoxyuridine of thisinvention shows the effective dose (EDs), which is required of thecompound for reducing the number of plaques formed on virus by 50%experimented with the use of a cell strain obtained by inoculating theVero cells with 10,000 pfu/ml of herpes simplex type I (KOS strain), aslow as about 1/400 (0.018 μg/ml) of Acyclovia for obtaining the sameeffect. The therapeutic index, which is indicated by the value of aratio of the minimum toxic dose (MTD), which shows the toxicity tonormal cells, to EDs, is 5,600, being remarkably high as compared with140 of Acyclovir.

The ester derivatives of 5-halogenated-2'-deoxyuridine of this inventionare administered orally or parenterally such as subcutaneously,intramuscularly, intravenously, intra-arterially, percutaneously,intrarectally, as eye drops, intravaginally, intrauterinely, andintracerebrally.

As the dosage form for oral administration, a tablet, pill, granule,powder, liquid preparation, suspension, and capsule, for instance, maybe mentioned.

Tablets are prepared according to an ordinary method with the use ofsuch excipients as lactose, starch, crystalline cellulose, andhydroxypropyl cellulose; such binders as carboxymethyl cellulose, methylcellulose, polyvinylpyrrolidone, and sodium alginate; and suchdisintegrators as calcium carboxymethyl cellulose and starch. Pills,powder, and granules can also be prepared according to an ordinarymethod with the use of the aforementioned excipients, etc. Liquidpreparations and suspensions are prepared according to an ordinarymethod with the use of such glycerol-esters as tricaprylin, triacetin,and trilaurin; such vegetable oils as coconuts oil and fractionatedcoconuts oil and such alcohols as ethanol. Capsules are prepared byfilling hard gelatin capsules with granules or powder, or by fillingsoft elastic gelatin capsules with a liquid preparation.

As the dosage form for the subcutaneous, intramuscular, intracerebral,intravenous, and intra-arterial administration use, there is aparenteral injection in the form of an aqueous or nonaqueous liquidpreparation or suspension. In preparing a nonaqueous liquid preparationor suspension, propylene glycol, polyethylene glycol, olive oil, andethyl oleate are used and an antiseptic and stabilizer are addedthereto, if necessary. An injection is usually sterilized by filtrationby means of bacterial filter method or by addition of an antimicrobialas case may require.

As the dosage form for percutaneous administration, ointments andcreams, for instance, may be mentioned. Ointments are manufacturedaccording to an ordinary method with the use of such fatty oils ascastor oil and olive oil, and vaseline. Creams are manufacturedaccording to an ordinary method with the use of fatty acid and suchemulsifying agents as diethylene glycol and sorbitan monofatty acidester.

Soft elastic gelatin capsules or suppositories prepared with the use ofcacao butter are used for intrarectal, intravaginal, and intrauteraladministration.

As the dosage form for application to eyes, eye drops and emulsion eyedrops prepared with the use of a boric acid solution, or eye ointmentsprepared with the use of vaseline or liquid paraffin may be mentioned.

The dose of the ester derivative of 5-halogenated-2'-deoxy uridine ofthis invention varies depending upon the age, sex, condition of apatient, and dosage form; however, it is usually in the range of 0.002to 2.0 mg/kg/day, preferably 0.01 to 1.0 mg/kg/day.

The amount of the ester derivative of 5-halogenated-2'-deoxyuridine tobe contained in the pharmaceutical preparations of this invention isdetermined based on the aforementioned dose. For example, a capsule,injection, and suppository are ordinarily made to contain 0.1 to 100 mg,preferably 0.2 to 50 mg of the ester derivative of5-halogenated-2'-deoxyuridine respectively.

The ester derivative of 5-halogenated-2'-deoxyuridine of this inventioncan be administered in combination of appropriately selected two or moreof its kinds.

The present invention is further described in detail by the followingreferential examples and examples.

REFERENTIAL EXAMPLE 1 Synthesis of3',5'-dioctanoyl-5-fluoro-2'-deoxyuridine

A solution was obtained by dissolving 250 mg (1.01 m mole) of5-fluoro-2'-deoxyuridine in 10 ml of pyridine anhydride and 590 mg (2.2m mole) of octanoic acid anhydride and 1.2 mg (0.01 m mole) ofdimethylaminopyridine were added thereto with stirring on the ice bath.The mixture was then stirred at room temperature overnight. The reactionmixture was poured into 50 ml of ice water and stirred for 30 minutes.Thereafter, 2N HCl was added to the reaction mixture to adjust its pHvalue to 4.0 and was then extracted three times with 20 ml of ethylacetate. Ethyl acetate was removed by distillation at room temperatureunder reduced pressure and the obtained crude product was dissolved indichloromethane and subjected to column chromatography on silica gel.The eluates from dichloromethane-ethanol (97:3)-(96:4) were collectedand concentrated to obtain 3',5'-dioctanoyl-5-fluoro-2'-deoxyuridine.

The physical properties of this substance are as follows:

UV spectrum (ethanol) λ mas 213, 281 nm

(2) ¹ H-NMR spectrum (chloroform-d) 6 value:

0.8-0.9 (6H, t--CH₃), 1.2-1.4 (20H, m, β-CH₂), 1.6-1.7 (4H, m, α-CH₂),2.4-2.6 (2H, m, C₂ '), 4.3-4.5 (3H, m, C₄ ', C₅ '),

5.2-5.4 (1H, m, C₃ '), 6.3 (1H, t, C₁ '), 7.9 (1H, d, J=6.5Hz, C₆)

REFERENTIAL EXAMPLE 2

Synthesis of 3',5'-didecanoyl-5-fluoro-2'-deoxyuridine

A solution of 250 mg (1.01 m mole) of 5-fluoro-2'-deoxy uridine in 10 mlofpyridine anhydride was prepared and 720 mg (2.2 m mole) of decanoicacid anhydride and 1.2 mg (0.01 m mole) of dimethylaminopyridine wereadded to the solution with stirring on the ice bath. The mixture wasthen stirred at room temperature overnight. After the reaction mixturewas poured into 50 ml of ice water and stirred for 30 minutes, themixture had its pH adjusted to 4.0 with 2N HCl and was extracted threetimes with 20 ml of ethyl acetate. The crude product obtained after theremoval of ethyl acetate by distillation at room temperature underreduced pressure was dissolved in dichloromethane and subjected tocolumn chromatography on silica gel. The eluates fromdichloromethane-ethanol (97:3)-(96:4) were pooled and concentrated togive 3',5'-didecanoyl-5-fluoro-2'-deoxyuridine.

The physical properties of this substance are as follows:

(1) UV spectrum (ethanol) λ max 213, 281 nm

(2) ¹ H-NMR spectrum (chloroform-d) δvalue:

0.8-0.9 (6H, t, --CH₃), 1.2-1.4 (28H, m, β-CH₂), 1.6-1.7

(4H, m, α-CH₂), 2.4-2.6 (2H, m, C₂ '), 4.3-4.5 (3H, m, C₄ ', C₅ '),5.2-5.4 (1H, m, C₃ '), 6.3 (1H, t, C:'),'7.9 (1H, d, J=6.5Hz, Cs)

Synthesis of 3,5'-didodecanoyl-5-fluoro-2'-deoxyuridine

A solution was prepared by dissolving 250 mg (1.01 m mole) of5-fluoro-2'-deoxyuridine in 10 ml of pyridine anhydride and 840 mg (2.2m mole) of dodecanoic acid anhydride and 1.2 mg (0.01 m mole) ofdimethylaminopyridine were added thereto with stirring on the ice bath.The admixture was further stirred overnight at room temperature. Thereaction mixture was poured into 50 ml of ice water and stirred for 30minutes. Thereafter the reaction mixture's pH was adjusted to 4.0 byadding 2N HCl and it was extracted three times with 20 ml of ethylacetate. Ethyl acetate was then distilled away at room temperature underreduced pressure and the resulting crude product was dissolved indichloromethane. The solution was subjected to column chromatographyover silica gel and eluates from dichloromethane ethanol (98:2)-(97:3)were collected and concentrated to obtain3',5'-didodecanoyl-5-fluoro-2'-deoxyuridine.

This substance has the following physical properties:

(1) UV spectrum (ethanol) λ max 213, 281 nm

(¹ H-NMR spectrum (chloroform-d) δ value:

0.8-0.9 (6H, t, --CH₃), 1.2-1.4

(36H, m, β-CH₂), 1.6-1.7 (4H, m, α-CH₂), 2.4-2.6 (2H, m, C₂ '), 4.3-4.5(3H, m, C₄ ', C₅ '), 5.2-5.4 (1H, m, C₃ '), 6,3 (1H, t, C₁ '), 7.9 (1H,d, J=6.5 Hz, C₆)

(3) Melting point: 49°-50° C.

REFERENTIAL EXAMPLE 4 Synthesis of3',5'-ditetradecanoyl-5-fluoro-2'-deoxyuridine

A solution of 250 mg (1.01 m mole) of 5-fluoro-2'-deoxyuridine in 10 mlof pyridine anhydride was prepared and then 960 mg (2.2 m mole) oftetradecanoic acid anhydride and 1.2 mg (0.01 m mole) ofdimethylaminopyridine were added thereto with stirring while coolingwith ice. The mixture was kept stirring over night at room temperature.After the reaction mixture was poured into 50 ml of ice water andstirred for 30minutes, 2N HCl was added thereto to adjust its pH to 4.0and the mixture was extracted three times with 20 ml of ethyl acetate.Ethyl acetate was removed by distillation at room temperature underreduced pressure and theobtained crude product was dissolved indichloromethane. The solution was subjected to column chromatographyover silica gel and the eluates obtained from dichloromethane-ethanol(98:2)-(97:3) were pooled and concentrated to give3',5'-ditetradecanoyl-5-fluoro-2'-deoxyuridine.

This substance has the following physical properties:

(1) UV spectrum (ethanol) λ max 213, 281 nm

(2) ¹ H-NMR spectrum (chloroform-d) δ value:

0.8-0.9 (6H, t, --CH₃), 1.2-1.4 (44H, m, β-CH₂), 1.6-1.7 α-CH₂), 2.4-2.6(2H, m, C₂ '), 4.3-4.5 (3H, m, C₄ ', C₅ '), 5.2-5.4 (1H, m, C₃ '), 6.3(1H, t, C₁ '), 7.9 (1H, d, J=6.5 Hz, C₆)

(3) Melting point: 65-67° C.

REFERENTIAL EXAMPLE 5

Synthesis of 3',5'-dihexadecanoyl-5-fluoro-2'-deoxyuridine

A solution was prepared by dissolving 250 mg (1.01 m mole) of5-fluoro-2'-deoxyuridine in 10 ml of pyridine anhydride, and 1100 mg(2.2 m mole) of hexadecanoic acid anhydride and 1.2 mg (0.01 m mole) ofdimethylaminopyridine were added to the solution with stirring on theice bath. The mixture was stirred overnight at room temperature. Thereaction mixture was poured into 50 ml of ice water, stirred for 30minutes, and its pH was adjusted to 4.0 by adding 2N HCl. Extraction wasrepeated threetimes with the use of 20 ml of ethyl acetate, and thenethyl acetate was distilled away at room temperature under reducedpressure. Thus obtained crude product was dissolved in dichloromethaneand the solution was put tocolumn chromatography on silica gel. Theeluates from dichloromethane-ethanol (98:2)-(97:3) were collected andconcentrated to obtain 3,5'-dihexadecanoyl-5-fluoro-2'-deoxyuridine.

This substance has physical properties as mentioned below:

(1) UV spectrum (ethanol) λ max 213, 281 nm

(2) ¹ H-NMR spectrum (chloroform-d) δ value 0.8-0.9 (6H, t, --CH₃),1.2-1.4 (52H, m, 8-CH), 1.6-1.7 (4H, m, u-CH), 2.4-2.6 (2H, m, C'),4.3-4.5 (3H, m, C', C'), 5.2-5.4 (1H, m, C'), 6.3 (1H, t, C'), 7.9(1H,e, J=6.5 Hz, Cs)

Melting point: 74°-75° C.

REFERENTIAL EXAMPLE 6 Synthesis of3',5'-dibenzoyl-5-fluoro-2'-deoxyuridine

A solution was prepared by dissolving 250 mg (1.01 m mole) of5-fluoro-2'-deoxyuridine in 10 ml of pyridine anhydride, and 500 mg (2.2mmole) of benzoic anhydride and 1.2 mg (0.01 m mole) ofdimethylaminopyridine were added thereto with stirring while beingcooled with ice. The mixture was stirred overnight at room temperature.The reaction mixture was poured into 50 ml of ice water and, after 30minutes'stirring, pH of the mixture was adjusted to 4.0 with 2N HCl andwas extracted three times with 20 ml of ethyl acetate. Methyl acetatewas distilled away at room temperature under by diminished pressure andthe resulting crude product was dissolved in dichloromethane to besubjected to column chromatography over silica gel. The eluates fromdichloromethane-ethanol (98:2)-(97:3) were pooled and concentrated toobtain 3',5'-dibenzoyl-5-fluoro-2'deoxyuridine. The yield was 85%.

This substance has the following physical properties:

(1) UV spectrum (ethanol) λ max 267, 230 nm

(2) ¹ H-NMR spectrum (chloroform-d: methanol-d₄ (1:1)) δ value: 25-4.502.40-2.60 (2H, m, C₂ ), 4.25-4.50 (3H, m, C₄ ', C₅ '), 5.1-5.40

(1H, m, C₃ '), 6.25 (1H, t, Cl'), 7.30-7.60 (6H, m, benzoyl), 7.90 (1H,d, J=6.5 Hz, C₆) 8.00-8.15 (4H, m, benzoyl-β-CH)

(3) Melting point: 273°-274° C.

REFERENTIAL EXAMPLE 7

Synthesis of 3',5'-dioctanoyl-5-iodo-2'-deoxyuridine

A solution was prepared by dissolving 350 mg (0.99 m mole) of5-iodo-2'-deoxyuridine in 5 ml of pyridine anhydride, and 600 mg (2.22 mmole) of octanoic anhydride and 1.2 mg (0.01 m mole) ofdimethylaminopyridine were added to the solution with stirring on theice bath. The mixture was kept stirring overnight at room temperature.The reaction mixture was poured into 50 ml of ice water, stirred for 30minutes, and then had its pH value adjusted to 4.0 with 2N NCl.Thereafter, the mixture was extracted three times with 20 ml ofchloroform. Chloroform was removed by distillation at room temperatureunder reduced pressure and the obtained crude product was dissolved indichloromethane and subjected to column chromatography on silica gel.The eluates obtained from dichloroethane-ethanol (99:1)-(98:2) werepooled andconcentrated to obtain 3',5')dioctanoyl-5-iodo-2'-deoxyuridine. The yield was 90%.

The physical properties of this substance are as follows:

(1) UV spectrum (ethanol) λ max 281, 213 nm

¹ H-NMR spectrum chloroform-d) δ value:

0.80 (6H, t, --CH₃), 1.05-1.70 (24H, m, --CH₂ --), 2.10-2.70 (6H,m, C₂', --CO--CH₂ --), 4.05-4.30 (3H, m, C₄ ', C₅ '), 5.10-5.20 (1H, m, C₃'), 6.20 (1H, t, Cl'), 7.85 (1H, s, C₆)

EXAMPLE 1

Vero cells were cultured in Eagle minimum essential medium (MEM)containing5% calf serum (CS) and were made to proliferate by means ofmonolayer cell culture. The cells were inoculated with 0.1 ml of herpessimplex type I virus (KOS strain) adjusted to 1,000 pfu/ml, which wereallowed to hold onthe host cells by adsorption for 1 hour at 37° C.Thereafter, the test compound, inclusive of the compounds of thisinvention, were added thereto respectively in concentration of0.01˜1,000 μg/ml.

After 48-hour culture in CS-MEM medium was over, the effective dose ofeachtest compound which suppressed the formation of plaques by 50% innumber (ED₅₀) and the minimum toxic dose (MTD) which caused thecytotoxicitywere measured.

The result is shown in Table 1.

                                      TABLE 1                                     __________________________________________________________________________                                       Therapeutic                                                                   index                                      Test compound        ED.sub.5 0                                                                           MTD    MTD/ED.sub.5 0                             __________________________________________________________________________    9-(2-hydroxyethoxymethyl)guanine                                                                   0.991 μg/ml                                                                       1,000 μg/ml                                                                       1,000                                      (Acyclovir)                                                                   (Control compound)                                                            5-fluoro-2'-deoxyuridine                                                                           0.01 μg/ml                                                                        0.1 μg/ml                                                                         10                                         (Control compound)                                                            3',5'-didodecanoyl-5-fluoro-2'-deoxyuridine                                                        0.054 μg/ml                                                                       100 μg/ml                                                                         1,900                                      (Compound of this invention)                                                  3',5'-ditetradecanoyl-5-fluoro-2'-deoxyuridine                                                     0.049 μg/ml                                                                       100 μg/ml                                                                         2,000                                      (Compound of this invention)                                                  3',5'-dihexadecanoyl-5-fluoro-2'-deoxyuridine                                                      0.077 μg/ml                                                                       150 μg/ml                                                                         2,000                                      (Compound of this invention)                                                  __________________________________________________________________________

EXAMPLE 2

Vero cells were cultured in Eagle minimum

1 medium (MEM) containing 5% calf serum (CS) and were made toproliferate after the monolayer cell culture method. The cultured cellswere inoculated with 0.1 ml of herpes simplex type I virus (KOS strain)of 10,000 pfu/ml concentration, which were left to be adsorbed by thehost cells at 37° C. for 1 hour. The test compounds, inclusive of thecompounds of this invention, were added to the cultures respectively inconcentration of 0.001˜1,000 μg/ml.

After 48-hour culture in 2% CS-MEM medium was over, the effective doseof each test compound which suppressed the formation of plaques by 50%in number (EDs) and the minimum toxic dose (MTD) which caused thecytotoxicity were measured.

The result is shown in Table 2.

                                      TABLE 2                                     __________________________________________________________________________                                     Therapeutic                                                                   index                                        Test compound      ED.sub.5 0                                                                           MTD    MTD/ED.sub.5 0                               __________________________________________________________________________    9-(2-hydroxyethoxymethyl)guanine                                                                 7.259 μg/ml                                                                       1,000 μg/ml                                                                       140                                          (acyclovir)                                                                   (Control compound)                                                            3',5'-dioctanoyl-5-fluoro-2'-deoxyuridine                                                        0.018 μg/ml                                                                       100 μg/ml                                                                         5,600                                        (Compound of this invention)                                                  3',5'-didecanoyl-5-fluoro-2'deoxyuridine                                                         0.038 μg/ml                                                                       100 μg/ml                                                                         2,600                                        (Compound of this invention)                                                  __________________________________________________________________________

EXAMPLE 3

Vero cells. were cultured in Eagle essential medium (MEM) containing 5%fetal calf serum (FCS) and were made to proliferate after the monolayercell culture method. The cells were inoculated with 0.1 ml of herpessimplex type I virus (KOS strain) of 2,000 pfu/ml concentration, whichwere made to be adsorbed by the host cells at 37° C. for 1 hour. Thevirus that were not yet adsorbed were washed away with a 2% CS-MEMmedium and then test compounds, inclusive of the compounds of thisinvention, were added to the cultures respectively in concentration of0.01˜1,000 μg/ml.

After 48-hour culture in 2% CS-MEM medium was over, the effective doseof each test compound which suppressed the formation of plaques by 50%in number (ED₅₀) and the minimum toxic dose (MTD) which caused thecytotoxicity were measured.

The result is shown in Table 3.

                                      TABLE 3                                     __________________________________________________________________________                                     Therapeutic                                                                   index                                        Test compound      ED.sub.5 0                                                                           MTD    MTD/ED.sub.5 0                               __________________________________________________________________________    9-(2-hydroxyethoxymethyl)guanine                                                                 3.363 μg/ml                                                                       1,000 μg/ml                                                                       279                                          (Acyclovir)                                                                   (Control compound)                                                            3',5'-dibenzoyl-5-fluoro-2'-deoxyuridine                                                         0.112 μg/ml                                                                       100 μg/ml                                                                         893                                          (Compound of this invention)                                                  3',5'-dioctanoyl-5-iodo-2'-deoxyuridine                                                          0.285 μg/ml                                                                       10 μg/ml                                                                          35                                           (Control compound)                                                            __________________________________________________________________________

As seen from Table 1, Table 2, and Table 3, the compound of thisinvention suppresses the proliferation of herpes simplex virus type Ieven at remarkably low concentration and also shows a very hightherapeutic index which is expressed by a ratio of the toxicity againstnormal cells to the antiviral activity as compared with Acyclovia and5-fluoro-2'-deoxyuridinethat is 5-halogenated-2'deoxyuridine not inducedto an ester derivative, which are now clinically used as the antiviraldrug.

EXAMPLE 4

Manufacture of capsules

The following ingredients were mixed to prepare powder and capsulesfilled with thus prepared powder were manufactured according to theordinary method.

    ______________________________________                                        Compound of this invention                                                                            10     mg                                             (3',5'-dihexadecanoyl-5-                                                      fluoro-2'-deoxyuridine)                                                       Lactose                 97     mg                                             Crystalline cellulose   50     mg                                             Magnesium stearate      3      mg                                             Total                   160    mg                                             ______________________________________                                    

EXAMPLE 5 Manufacture of injections

A compound (3',5'-ditetradecanoyl-5-fluoro-2'-deoxyuridine) of thisinvention was dissolved in distilled water for injection (pH 6.00˜7.50)to obtain an injection containing 0.3˜1 mg of the compound per ml.

EXAMPLE 6 Manufacture of ointments

The following ingredients were thoroughly mixed and made into anointment according to the ordinarily practiced method.

    ______________________________________                                        Compound of this invention                                                                             0.1   g                                              (3',5'-dioctanoyl-5-fluoro-                                                   2'-deoxyuridine)                                                              Diisopropyl adipate      2.0   g                                              White soft paraffine     7.9   g                                              Total                    10    g                                              ______________________________________                                    

EXAMPLE 7 Manufacture of suppositories

The following ingredients were mixed well and formed into suppositoriesaccording to the ordinary method.

    ______________________________________                                        Compound of this invention                                                                             5      mg                                            (3',5'-didecanoyl-5-fluoro-2'-                                                deoxyuridine)                                                                 Witepsol                 1,995  mg                                            (manufactured by Dynamit Nobel)                                               (consisting of C.sub.12 -C.sub.18 mono-,                                      di-, and tri-glycerides)                                                      Total                    2,000  mg                                            ______________________________________                                    

EXAMPLE 8

Manufacture of eye ointments

The following ingredients were mixed to prepare an eye ointmentaccording to the ordinary method.

    ______________________________________                                        Compound of this invention                                                                             0.1    g                                             (3',5'-didodecanoyl-5-                                                        fluoro-2'-deoxyuridine)                                                       Vaseline                 7.0    g                                             Liquid paraffin          2.9    g                                             Total                    10     g                                             ______________________________________                                    

Industrial Applications

An antiviral agent which contains a 5-halogenated-2'-deoxyuridinederivative of the present invention as the active ingredient displays ahigh level of antiviral effect with small doses and yet its toxicity tonormal cells is low and accordingly can be used for the therapy ofvariouskinds of viral infections.

We claim:
 1. A method of inhibiting herpes simplex type I viralreplication in a cell comprising administering an effective amount toinhibit herpes simplex type I viral replication in a cell of anesterified derivative of a 5-halogenated-2,'-deoxy-uridine expressed bythe following formula ##STR3## wherein X represents any one of F, Cl,and Br; R¹ and R₂ may be identical or different from each other, eachrepresenting a straight chain saturated aliphatic acyl group comprisingeight to sixteen carbon atoms.
 2. The method of claim 1, wherein X informula (I) is a fluorine atom.